1. Technical Field
The present invention is directed toward windows, and more particularly toward a structure for controlling operation of a sash of a double hung window.
2. Background Art
Double hung windows are well known in the art, and include a pair of sashes generally movable in parallel planar paths whereby the window opening may be half opened by moving one sash into an overlapping position with the other sash. Typically, such operation is accomplished by raising and lowering the inner sash (i.e., the sash moving in the path closest to the interior of the room) with the outer sash being generally secured at the upper end of its path. In ideal double hung windows, it is preferable that there be an ability to easily remove the sash for maintenance as well as (as is becoming increasingly popular) an ability to tilt in the bottom sash so that the outer surface of its pane may be reached from the interior of the room for washing.
Locking is typically provided by cam locks, such as check rail locks, in which the two sashes are mechanically secured to one another when in the closed non-overlapping position to prevent movement relative to one another. Such locks are generally required to be disposed on top of the lower sash, which in some installations can be difficult to reach (for example, with tall window sashes or windows located higher on the wall than normal).
Such locks are also susceptible to breaking when forced in that the entire locking occurs at the particular location of the lock. Therefore, if an intruder tries to force the window, the entry force is resisted solely at the one point (where the sash lock is secured to the sash). Breaking of the lock, or particularly the wooden or PVC sash, is thus a distinct possibility due to the resulting stress concentrations at the lock location.
Still further, since such locks are generally disposed in the middle of the opening, they can be an undesirable visual intrusion on the view through the glass in the upper sash. One structure which has been used in order to minimize such a visual intrusion is the concealed check rail lock disclosed in U.S. Pat. No. 4,813,725, but even that advantageous structure requires that the handle be accessible and therefore visible.
Counterbalancing weights or compensating springs are also typically used with sashes of double hung windows to make it easier for a person to raise such sashes. The sashes are typically held in open venting positions by a combination of the counterbalancing weights or springs and some frictional binding of the sash in its track. Of course, such necessary binding also, unfortunately, also occurs when moving the sash to thereby increase the effort required to open and close the window. There is, therefore, typically some design balance which is required between minimizing binding to ease operation while maintaining some amount of binding to prevent the sash from falling closed (and possibly injuring a person, particularly a child, who might have their hands or head in the opening). Of course, even a proper initial design balance will often fail over time, as evidenced by the not uncommon occurrence of older windows which today are kept open only by wedging something such as a board beneath the sash (in which case, people typically will open the window to one venting position--that provided by the board they have next to the window).
While the connection of the moving sash to the frame is obviously important to operation of the window as discussed above, it is also an area which is susceptible to undesirable air drafts and energy loss, since tight connections between the frame and the sash to prevent such loss would undesirably tend to bind the sash to the frame and thereby significantly increase the force required to move the sash. Such constraints similarly tend to limit the types of gaskets which can be used to try to reduce the energy loss between the sash and the frame.
Other structures have been used, typically in storm windows, in which the sash may be mechanically secured in a variety of raised positions by outwardly biased pins receivable in openings spaced along the track. Such structures when properly operating will secure the sash at a discrete number of venting positions. However, they are difficult to operate as operation of the sash typically requires that the person pull in the pins on both sides of the sash while moving the sash. Further, such structures are susceptible to failure as can occur when dirt and grime binds the pin against extending outwardly into a locking position, or if the pin is not properly seated in the track openings (in which case, just a little bump could cause the sash to fall and damage the sash and anything under it).
The present invention is directed toward overcoming one or more of the problems set forth above.